mirror of
https://github.com/nim-lang/Nim.git
synced 2025-12-29 09:24:36 +00:00
86f7f4ffa5
* remove deprecated pragma syntax from 0.20.0 closes #4651, closes #16653 with a cheap fix for now due to how early `tfFinal` is set * remove type pragma between name and generics * undo removal, try removing bind expression (0.8.14) * fix test, unremove bind expr * remove again * Update changelog.md Co-authored-by: konsumlamm <44230978+konsumlamm@users.noreply.github.com> * dependencies @ HEAD & weave test dependencies * try fix package ci Co-authored-by: konsumlamm <44230978+konsumlamm@users.noreply.github.com>
75 lines
1.5 KiB
Nim
75 lines
1.5 KiB
Nim
discard """
|
|
output: '''
|
|
OBJ 1 foo
|
|
10
|
|
OBJ 1 bar
|
|
OBJ 2 foo
|
|
5
|
|
OBJ 2 bar
|
|
'''
|
|
"""
|
|
|
|
type
|
|
# these are the signatures of the virtual procs for each type
|
|
fooProc[T] = proc (o: var T): int {.nimcall.}
|
|
barProc[T] = proc (o: var T) {.nimcall.}
|
|
|
|
# an untyped table to store the proc pointers
|
|
# it's also possible to use a strongly typed tuple here
|
|
VTable = array[0..1, pointer]
|
|
|
|
TBase {.inheritable.} = object
|
|
vtbl: ptr VTable
|
|
|
|
TUserObject1 = object of TBase
|
|
x: int
|
|
|
|
TUserObject2 = object of TBase
|
|
y: int
|
|
|
|
proc foo(o: var TUserObject1): int =
|
|
echo "OBJ 1 foo"
|
|
return 10
|
|
|
|
proc bar(o: var TUserObject1) =
|
|
echo "OBJ 1 bar"
|
|
|
|
proc foo(o: var TUserObject2): int =
|
|
echo "OBJ 2 foo"
|
|
return 5
|
|
|
|
proc bar(o: var TUserObject2) =
|
|
echo "OBJ 2 bar"
|
|
|
|
proc getVTable(T: typedesc): ptr VTable =
|
|
# pay attention to what's going on here
|
|
# this will initialize the vtable for each type at program start-up
|
|
#
|
|
# fooProc[T](foo) is a type coercion - it looks for a proc named foo
|
|
# matching the signature fooProc[T] (e.g. proc (o: var TUserObject1): int)
|
|
var vtbl {.global.} = [
|
|
cast[pointer](fooProc[T](foo)),
|
|
cast[pointer](barProc[T](bar))
|
|
]
|
|
|
|
return vtbl.addr
|
|
|
|
proc create(T: typedesc): T =
|
|
result.vtbl = getVTable(T)
|
|
|
|
proc baseFoo(o: var TBase): int =
|
|
return cast[fooProc[TBase]](o.vtbl[0])(o)
|
|
|
|
proc baseBar(o: var TBase) =
|
|
cast[barProc[TBase]](o.vtbl[1])(o)
|
|
|
|
var a = TUserObject1.create
|
|
var b = TUserObject2.create
|
|
|
|
echo a.baseFoo
|
|
a.baseBar
|
|
|
|
echo b.baseFoo
|
|
b.baseBar
|
|
|